In the current study of gastrointestinal (GI) function and symptoms in menstruating women, approximately 30% reported symptoms compatible with irritable bowel syndrome (IBS). IBS is characterized by upper and,/or lower abdominal pain and change in defecation pattern in the absence of overt pathology, accounts for 100,000 hospital discharges per year and 30-70% of visits to gastroenterologists. Preliminary analysis of our current sample has shown that autonomic nervous system (ANS) arousal, menstrual cycle phase, and psychological distress are associated with such symptoms. Specifically, women who reported recurrent GI symptoms exhibited higher urine catecholamine levels, higher anxiety and more ANS arousal symptom levels particularly at menses. This continuation study is designed to characterize the patterning of GI symptoms with respect to menstrual cycle function, ANS/adrenal arousal, psychological and somatic distress and GI function in menstruating women between 20-40 years of age. Comparisons will be made with 3 groups of women: 1) those with medically diagnosed IBS, 2) those with IBS-like symptoms but not medically diagnosed, and 3) asymptomatic or control. Women will be studied at 3 phases (i.e., menses, follicular, luteal) of the menstrual cycle for 2 menstrual cycles. Both physiological and self-report measures will be used to characterize patterns of GI function, ANS adrenal arousal, and distress. Further, this study includes using an animal model (Sprague-Dawley rat) to validate the, impact of experimentally controlled ovarian steroid hormones (i.e., estrogen, progesterone) on GI function. Both humans and animals will be studied under basal and acute stimulus conditions to examine the impact of stress arousal with varying ovarian hormone levels on GI function (rats) and ANS/adrenal arousal (humans and rats). Knowledge of the relationship among menstrual cycle function, ANS /adrenal arousal, psychological/somatic distress and GI responsivity (symptoms and function) has implications for GI symptom management in menstruating women.